In the field of mobile telecommunications, it is known for mobile communication units, such as mobile telephone handsets, to provide personal hands-free functionality in, say, a form of an audio headset. Traditionally, an accessory such as an audio headset may be connected to the mobile telephone handset via a wire, one end of which comprises, for example, a jack that plugs into a socket provided by the mobile telephone handset. More recently, wireless audio headset accessories have become popular, in particular in a form of Bluetooth™ headsets. Consequently, current mobile telephone handsets are required to provide wired and wireless audio headset capabilities. Furthermore, such handsets are required to provide wired and wireless audio attach signalling capabilities.
It has also become a commercial requisite for wireless (audio) attach functionality to comprise a visual indication of a status of wireless functionality, typically in a form of a blue light emitting diode (LED), which requires a boosted positive voltage (namely a voltage greater than a voltage available from the handset battery source).
FIG. 1 illustrates an example of voltage supply circuitry for wired audio headset functionality 110 and for a visual indication 120 of a status of wireless functionality, for example within a mobile communication unit, as is known in the art. Due to their respective voltage requirements, the wired audio headset functionality 110 and the visual indication element 120 are each provided with a dedicated voltage supply.
For the illustrated example, the voltage supply for the wired audio headset functionality 110 comprises a voltage regulator 115, operatively coupled to a 3.6 v voltage supply (Vbat) supplied from a battery source (not shown). The voltage regulator 115 provides the wired audio headset functionality 110 with a supply voltage (Vaudio) of 2.8 v. The wired audio headset functionality 110 provides two audio outputs for a headset coupled thereto. Each output is coupled to a headset via a coupling capacitor 117 to remove a DC (direct current) offset. Typically, wired audio headset functionality requires a positive voltage supply and a negative voltage supply for a capacitor-less coupled audio amplifier implementation.
The voltage supply for the visual indication element 120 of a wireless operation comprises Boost or Charge Pump circuitry 125, which is also coupled to the voltage supply (Vbat) from the battery. The Boost/Charge Pump circuitry 125 provides the visual indication element 120 with a boost voltage (Vboost) of, say, 5.5 v. The boost voltage (Vboost) is provided to the visual indication element 120, which is also coupled to a driver circuit 127.
The voltage supply circuitry for wired audio headset functionality 110 and for visual indication element 120 of a wireless operation may be provided on a semiconductor device 130, such as an integrated circuit. Also illustrated is DC/DC converter circuitry 140, arranged to provide a 1.8 v voltage supply (Vmem) to, for example, memory components, or other components of the mobile communication unit. As will be appreciated, the provision of a dedicated voltage supply for each of the wired audio headset functionality 110 and for the visual indication element 120 of the status of wireless functionality is consuming in terms of silicon area, and is also expensive in terms of component count.
As more sophisticated functionality permeates its way down to lower tier mobile telephone handsets, the need to provide such functionality, whilst keeping the size and cost of the handset as low as possible, increases. Thus, a need exists for an improved voltage supply circuitry for wired audio headset functionality circuitry that is also able to support visual indication circuitry for wireless (headset) attach signalling functionality, for example within a mobile communication unit.